Warning placards are required to be used any time a vehicle is carrying designated types and amounts of hazardous materials. A placarded vehicle must display placards on all four of its sides.

You should always slow down to a safe speed and shift into a lower gear before entering a curve.

Some air brake systems include an alcohol evaporator. The evaporator introduces alcohol into the braking system to prevent the formation of ice, which can cause damage.

It is important to inspect your tires before every drive. Rust around wheel nuts may indicate that they are loose.

The tractor protection valve keeps air in the trailer's braking system should the trailer break away or develop a leak. A loss of air pressure in the emergency line will cause the tractor protection valve to open and the emergency trailer brakes to activate.

An Anti-Lock Braking System (ABS) intervenes to reduce brake pressure if there is a risk of wheel lockup. If the ABS isn't working, the vehicle's basic braking functions are not affected. A driver should continue to drive and brake in a normal manner.

If your mirrors or wiper blades become icy while you are driving, you can expect the road surface to be icy as well.

The liver removes alcohol from the body at a fixed rate, so the only way to sober up after consuming alcohol is to allow your body time to remove the alcohol on its own.

If your trailer begins to skid, you should release the brakes to regain traction. The trailer will begin to straighten out once the wheels begin to grip the road again.

Be sure that you are able to accelerate without first rolling back. Rolling backwards may cause you to collide with a vehicle or other obstacle behind your truck.

After an engine is started, the coolant temperature should begin a gradual rise toward the normal operating range.

When performing a visual check of coupling devices, you should make sure there is no space between the upper and lower fifth wheel. Ensure that the locking jaws are securely closed around the kingpin.

If you see a distracted driver, give them plenty of space and maintain a safe following distance.

Slow down and be especially careful when driving in and around work zones, in places where the pavement drops off sharply at the edge of the road, when foreign objects are present on the road, and on freeway on- and off-ramps.

There are two air brake systems in a dual air brake system. The systems share a set of brake controls, but each system has its own tanks, hoses, and lines.

When backing up to couple a trailer, you should position the tractor directly in front of the trailer. Trying to couple while backing at an angle could cause the trailer to move and the landing gear to break.

The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. It should be used only to test the brakes. Using it while a vehicle is in motion could cause a skid.

When inspecting a vehicle that is equipped with power steering, check the hoses, pumps, and fluid level. In particular, you should look for leaks in the hoses.

The easiest way to become aware that your trailer has begun to jackknife is to observe it in your mirrors. Checking your trailer in your mirrors will also allow you to spot any skidding at the earliest possible moment.

If your drive wheels begin to spin while accelerating on a surface with poor traction, you should remove your foot from the accelerator.